Aminophosphine type ligands, such as aminophosphines, diaminophosphines, aminodiphosphines and diaminodiphosphines, represent an important class of ligand as evidenced by the wide range of transformations in which they can participate.1 As is often the case for phosphorus-based ligands2, these materials can be extremely sensitive to oxygen making them difficult to handle or even prepare. Fu et al. reported on the stabilization of reactive phosphines via quaternization with acid.3 The resulting phosphonium salts displayed remarkable stability toward oxygen and moisture while their utility in synthetic and catalytic applications remained highly convenient.
Several reports describing the use of quaternized P—N ligands have appeared however in all cases they were used exclusively as cationic ligands.4 